1. Technical Field
The present invention relates to a gap composition of a multilayered power inductor and a multilayered power inductor including a gap layer using the same.
2. Description of the Related Art
A multilayered power inductor has been mainly used for a power supply circuit such as a DC-DC converter within portable devices. Meanwhile, the multilayered power inductor has been developed to implement high current, low DC resistance, or the like, while being miniaturized. As a demand for high frequency and miniaturization of the DC-DC converter is increased, the use of the multilayered power inductor has been suddenly increased, instead of the existing wound choke coil.
The multilayered power inductor suppresses magnetic saturation of the inductor in terms of a material and a structure and thus, may be operated at high current. As compared with the wound power inductor, the multilayered power inductor increases a change in a value of inductance L according to applied current but may be manufactured in a small size and may lower a thickness and is advantageous in terms of DC resistance.
The structure of the general multilayered power inductor currently used is shown in FIG. 1. Referring to FIG. 1, the multilayered power inductor includes an inner electrode 10, a body 20 using a ferrite material, and a gap layer 30 in the body 20. The gap layer is inserted into the body to block a magnetic flux, which serves to reduce a change value in inductance according to applied current. The gap layer is sintered at about 900° C. and then, an external electrode 40 is formed and a plating layer 50 is formed using Ni, Sn, or the like, thereby finally manufacturing a multilayered power inductor.
The gap layer 30 of the general multilayered power inductor is formed by molding a sheet between inner electrode layers on a single plane and then, stacking a plurality of layers. In addition, the gap layer 30 extends to the external electrodes 40 formed at both outsides of the body 20. Therefore, the gap layer 30 contacting the external electrode 40 may be delaminated during a sintering process.
Generally, a magnetic structure of a magnetic circuit is broken by a non-magnetic body or an air gap, such that a magnitude in flowing magnetic flux is reduced due to the increase in magnetic resistance. Therefore, effective permeability is reduced and inductance is reduced accordingly. However, the change rate of the value of the inductance L is very small.
Therefore, in the general inductor, the change in inductance is directly proportional to the permeability. On the other hand, in the inductor having the gap layer, the influence of inductance according to the change in permeability is greatly suppressed. Therefore, DC-bias characteristics of the power inductor may be greatly improved by inserting the gap layer. However, when a product substantially uses the inductor, the inductor needs to satisfy DC-bias characteristics at room temperature and DC-bias characteristics (hereinafter, bias-TCL) according to a temperature change (−50 to −125° C.) such as below zero temperature and high temperature.
However, in the case of the power inductor including the gap layer having the structure according to the related art, temperature stability may be degraded due to the change in the inductance value according to the applied current by changing temperature.
The non-magnetic body used as the current multilayered power inductor gap material uses ferrite composition similar to the magnetic material configuring the body but mainly uses Zn—Cu based ferrite that does not contain NiO so as to remove magnetism. However, the Zn—Cu based ferrite has different temperature characteristics due to diffusion according to the temperature. A need exists for a gap material capable of improving the Bias-TCL characteristics.
Further, a need exists for a development of a new gap material and a development of a multilayered power inductor having a new structure capable of improving the Bias-TCL characteristics.